#pragma once

#include <linux/atomic.h>
#include <asm-generic/spinlock_types.h>

static __always_inline void ticket_spin_lock(arch_spinlock_t *lock)
{
    u32 val = atomic_fetch_add(1 << 16, &lock->val);
    u16 ticket = val >> 16;

    if (ticket == (u16)val)
        return;

    /*
     * atomic_cond_read_acquire() is RCpc, but rather than defining a
     * custom cond_read_rcsc() here we just emit a full fence.  We only
     * need the prior reads before subsequent writes ordering from
     * smb_mb(), but as atomic_cond_read_acquire() just emits reads and we
     * have no outstanding writes due to the atomic_fetch_add() the extra
     * orderings are free.
     */
    atomic_cond_read_acquire(&lock->val, ticket == (u16)val);
    smp_mb();
}

static __always_inline bool ticket_spin_trylock(arch_spinlock_t *lock)
{
    u32 old = atomic_read(&lock->val);

    if ((old >> 16) != (old & 0xffff))
        return false;

    return atomic_try_cmpxchg(&lock->val, &old, old + (1 << 16)); /* SC, for RCsc */
}

static __always_inline void ticket_spin_unlock(arch_spinlock_t *lock)
{
    u16 *ptr = (u16 *)lock + IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
    u32 val = atomic_read(&lock->val);

    smp_store_release(ptr, (u16)val + 1);
}

static __always_inline int ticket_spin_value_unlocked(arch_spinlock_t lock)
{
    u32 val = lock.val.counter;

    return ((val >> 16) == (val & 0xffff));
}

static __always_inline int ticket_spin_is_locked(arch_spinlock_t *lock)
{
    arch_spinlock_t val = READ_ONCE(*lock);

    return !ticket_spin_value_unlocked(val);
}

static __always_inline int ticket_spin_is_contended(arch_spinlock_t *lock)
{
    u32 val = atomic_read(&lock->val);

    return (s16)((val >> 16) - (val & 0xffff)) > 1;
}

#ifndef __no_arch_spinlock_redefine
/*
 * Remapping spinlock architecture specific functions to the corresponding
 * ticket spinlock functions.
 */
#define arch_spin_is_locked(l) ticket_spin_is_locked(l)
#define arch_spin_is_contended(l) ticket_spin_is_contended(l)
#define arch_spin_value_unlocked(l) ticket_spin_value_unlocked(l)
#define arch_spin_lock(l) ticket_spin_lock(l)
#define arch_spin_trylock(l) ticket_spin_trylock(l)
#define arch_spin_unlock(l) ticket_spin_unlock(l)
#endif
